Catalyst for deep oxidation of carbon oxide and organic compounds

ABSTRACT

A catalyst for the deep oxidation of organic compounds and carbon monoxide contains 2.7-11.5 mass. % of manganese (with respect to elementary manganese), balance alumina. Manganese stays as non-stoichiometric manganese oxide β-Mn 3  O 4+x , where 0.1≦×≦0.25, containing 80-95% of all manganese atoms, and as manganese aluminate containing 20-5% of manganese atoms. Alumina in the active component is presented by the high temperature forms α-Al 2  O 3  (72-95 catalyst mass. %) and (δ+θ)-Al 3  O 3  (28-05 catalyst mass. %). The catalyst active component has a monolith defect structure, particles size being 50-70 Å. Catalyst phase composition and structure form during its thermal treatment at 900°-1000° C.

FIELD OF ART

The present invention relates to chemistry and concerns the chemical and phase composition of catalysts for a deep oxidation of organic compounds and carbon oxide. The latter are present in industrial exhaust gases, exhausts of inner combustion engines, natural gas. The invention can be used to clean industrial and exhaust gases before their ejection into the atmosphere and to obtain calorific heat.

STATE OF ART

There are several well known catalysts that help to perform the oxidation of organics and carbon oxide. Such catalysts should exhibit a high thermal shock resistance, since heat evolves during the reaction and catalyst bed temperature attains 400°-1000° C. With this regard catalysts based on aluminium-manganese system are quite promising.

The known manganese oxide based catalysts contain phase oxides, mostly MnO₂, mixed or not mixed with the oxides of other elements (e.g., the hopkalite catalysts, see the FRG patent No 2010449, MKI BO1J 23/34). These catalysts are prepared either via support impregnation by the Mn(II) salts solutions or by moulding (e.g., extrusion) conditioned paste or charge containing the oxides of aluminium, copper or such compounds as calcium aluminate (Bakhtadze V. Sh. Manganese and Manganese-Copper Catalysts, PhD thesis, Tbilisi, 1971).

Such catalysts are calcined in special furnaces at 550°-850° C. They, however, exhibit a low activity. Thus, in a model reaction of n-pentane oxidation a catalyst sample prepared via alumina impregnation by manganese nitrate solution shows activity lower than 6×10⁻⁴ cm³ /(g s) at 30020 C. and current pentane concentration equal to 0.05 vol. %. X-ray phase analysis data and electron microscopy show that the phase composition of this sample includes rather large (up to 500 Å) particles of β-MnO2 and γ-Al₂ O₃.

It is possible to obtain aluminium-manganese catalyst for the deep oxidation of organic compounds and carbon oxide peptizing an acid mixture of a phase oxide Mn2O₃ with γ-Al₂ O₃, then extruding it, drying and calcining at 800° C. (Japan patent No 52-38977 MKI BO1 D 53/34). This catalyst also shows a low catalytic activity, since its active component has a low dispersity and is well crystallized.

Therefore, the known aluminium-manganese catalysts, though exhibiting a good thermal stability necessary for the process performance, have a low activity caused by a large size and thus small surface of the active component.

DISCLOSURE OF THE INVENTION

The present invention aims at designing a catalyst for the deep oxidation of organic compounds and carbon oxide. The catalyst should be resistant to heat and show a high activity. For the purpose the catalyst suggested has the following composition: 2.7-11.5 mass. % of manganese, balance alumina.

Manganese (Mn) in the active component is represented by a defect non-stoichiometric oxide β-Mn₃ O_(4+x), where 0.1<×<0.25, containing 80-95% of all manganese atoms and by manganese aluminate containing 20-5% of all manganese atoms. Alumina Al₂ O₃ is presented by the high temperature forms α and (δ+θ).

The catalyst of such phase and chemical composition is obtained via a high temperature treatment of moulded (extrudated) or impregnated catalyst at 900°-1000° C. During the thermal treatment initial solid solution Mn_(y) Oγ-Al₂ O₃ decomposes, and a disperse defect spinel phase Mn₃ O_(4+x) forms on the surface of generated high temperature aluminas as well as a solid solution based on manganese aluminate of non-identified composition.

The high temperature forms of alumina in the catalyst are represented by particles of irregular but round spatial configuration with a size of about 1000 Å. The defect spinel dispersed at the surface of the above particles consists of round agglomerated particles of non-stiochiometric manganese oxide having size of 400-500 Å. The two types of particles are fixed by the inteijacent layer. This layer is a product of an interaction between alumina and manganese oxide, namely the solid solution based on the manganese aluminate. Fixed position of the active manganese oxide at the surface of an alumina particle avoids fritting of the active component of the catalyst at high temperatures. Decreasing of the catalyst activity also drops down.

Electron microscopy shows that the active component particles attain 50-70 Å in size and have a segmented defect structure. This increases the catalyst surface dramatically and thus increases the catalyst activity as well.

A high performance electron microscopy and microdiffraction prove that manganese oxide with a defect spinel structure is present in the catalyst after its treatment in the temperature range mentioned.

Manganese oxidation degree in its oxide compounds is determined by a two-stage chemical analysis. The first stage is manganese oxide eluation by solution 0.1 N H₂ SO₄ +0.1 N KJ. At the second stage iodine evolved in the first stage is titrated by thiosulfate. The non-removed portion of manganese is a non-stoichiometric manganese aluminate of non-identified composition. Catalyst activity tested in two model reactions of deep oxidation of n-pentane and CO is by 5-10 fold higher than that of the known aluminium-manganese catalysts.

BEST MODE CARRYING-OUT THE INVENTION

The following examples help to understand the invention better.

EXAMPLE 1

159.2 g of aluminium hydroxide (pseudoboehmite modification) are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 6.4 g of manganese with respect to elementary manganese. The samples thus obtained stays for 24 h in air, then it is dried for 4 h at 120° C. The dried samples passes to a cold muffle, where it is slowly heated up to 900° C. during 3 h and then kept at this temperature for 4 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel comprising 87% of all manganese atoms                               7.7    mass. %     present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.3    mass. %     13% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               73.6   mass. %     alumina modification (δ + θ)-Al.sub.2 O.sub.3                               18.4   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 40. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 190° C.

EXAMPLE 2

153.9 g of aluminium hydroxide (pseudoboehmite modification) are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 9.5 g of manganese with respect to elementary manganese. The samples thus obtained stays for 24 h in air, then it is dried for 4 h at 120° C. The dried sample passes to a cold muffle, where it is slowly heated up to 900° C. during 3 h and then kept at this temperature for 4 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel comprising 90% of all manganese atoms                               11.6   mass. %     present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.9    mass. %     10% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               83.6   mass. %     alumina modification (δ + θ)-Al.sub.2 O.sub.3                               4.4    mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 40. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 187° C.

EXAMPLE 3

149.6 g of aluminium hydroxide (baierite modification) are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 12 g of manganese with respect to elementary manganese. The samples thus obtained stays for 24 h in air, then it is dried for 4 h at 120° C. The dried sample passes to a cold muffle, where it is slowly heated up to 1000° C. during 3 h and then kept at this temperature for 2 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel comprising 92% of all manganese atoms                               13.6   mass. %     present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.8    mass. %     8% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               85.6   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³) /(g_(cat) *s), where W is the oxidation rate, is equal to 45. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 185° C.

EXAMPLE 4

149.6 g of aluminium hydroxide (baierite modification) are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 12 g of manganese with respect to elementary manganese. The samples thus obtained stays for 24 h in air, then it is dried for 4 h at 120° C. The dried sample passes to a cold muffle, where it is slowly heated up to 90020 C. during 3 h and then kept at this temperature for 6 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel comprising 95% of all manganese atoms                               12.35  mass. %     present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.45   mass. %     5% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               76.4   mass. %     alumina modification (δ + θ)-Al.sub.2 O.sub.3                               10.8   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm3) /(g_(cat) *s), where W is the oxidation rate, is equal to 45. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 185° C.

EXAMPLE 5

175 g of the product of thermochemical activation of hydroargelite (or 75 mass. % if referred to Al₂ O₃) are mixed with 27.4 g of MnO₂ (or 17 g if referred to elementary manganese). Then 2.35 g of binder/reducer polyvinyl alcohol (PVA) and 4.7 ml of peptizing nitric acid (acid module is 0.055 if referred to Al₂ O₃) are added. The mixture obtained is stirred and the paste obtained goes to extrudation through a die to produce rings with external diameter of 12 mm. Then the rings are dried at 110° C. The dried rings are calcined first at 500° C., then at 950° C. for 6 h. The catalyst obtained has the following composition:

    ______________________________________     defect spinel comprising 80% of all manganese atoms                               12.5   mass. %     present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               2.2    mass. %     20% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               85.3   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 73. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 173° C.

EXAMPLE 6

87.5 g of the product of thermochemical activation of hydroargelite and 65.6 g of mechanoactivated powder of γ-alumina are mixed with 27.4 g of MnO₂ (or 17 g if referred to elementary manganese). Then 2.35 g of binder/reducer polyvinyl alcohol (PVA) and 4.7 ml of peptizing nitric acid (acid module is 0.055 if referred to Al₂ O₃) are added. The mixture obtained is stirred and the paste obtained goes to extrudation through a die to produce rings with external diameter of 12 mm. Then the rings are dried at 110° C. The dried rings are calcined first at 500° C., then at 95020 C. for 6 h. The catalyst obtained has the following composition:

    ______________________________________     defect spinel Mn.sub.3 O.sub.4.17 comprising 90% of all                               13.9anese                                      mass. %     atoms present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               1.1    mass. %     10% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               85.0   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm3)/(g_(cat) *s), where W is the oxidation rate, is equal to 61.35. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 175° C.

EXAMPLE 7

93.8 g of γ-alumina are impregnated by manganese nitrate solution containing 45.1 g of Mn(NO₃)₂ *H₂ O (or, 8.6 g with respect to elementary manganese). The sample thus obtained is dried for 1.5 h at 110° C. then calcined in the muffle at 900° C. for 10 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel Mn.sub.3 O.sub.4.1 comprising 85% of all manganese                               9.7    mass. %     atoms present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               1.2    mass. %     15% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               89.1   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 45. Catalyst activity towards CO expressed as the temperature of 50 % CO conversion is equal to 184° C.

EXAMPLE 8

100 g of alumina ((γ+θ)-Al₂ O₃ are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 6.12 g of manganese with respect to elementary manganese. The sample thus obtained stays for 24 h in air, then it is dried for 4 h at 12020 C. The dried sample passes to a cold muffle, where it is calcines at 900° C. for 6 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel Mn.sub.3 O.sub.4.2 comprising 95.1% of all                               8.1    mass. %     manganese atoms present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.4    mass. %     4.9% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               72.0   mass. %     alumina modification (δ + θ)-Al.sub.2 O.sub.3                               21.5   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 42. Catalyst activity towards CO expressed as the temperature of 50% CO conversion is equal to 186° C.

EXAMPLE 9

100 g of alumina α-Al₂ O₃ are impregnated by manganese nitrate solution till incipient wetness. When the solution fills the pores it contains 5.26 g of manganese with respect to elementary manganese. The sample thus obtained is dried for 4 h at 120° C. The dried sample is calcined at 900° C. for 2 h. The catalyst thus obtained has the following composition:

    ______________________________________     defect spinel Mn.sub.3 O.sub.4.2 comprising 94% of all manganese                               6.7    mass. %     atoms present in the catalyst sample     manganese in alumina (manganese aluminate) comprising                               0.4    mass. %     6% of all manganese atoms in the sample, referred to     elementary manganese     alumina modification α-Al.sub.2 O.sub.3                               92.7   mass. %     ______________________________________

The sample activity is tested in a flow-circulation setup in the model reactions of n-pentane and CO oxidation. Reactions occur at 300° C., current n-pentane concentration being 0.05 vol. %, current CO concentration being 1 vol. %. Catalyst activity towards n-pentane is expressed as (W*10⁴ ncm³)/(g_(cat) *s), where W is the oxidation rate, is equal to 50. Catalyst activity towards CO expressed as the temperature of 50 % CO conversion is equal to 180° C.

INDUSTRIAL APPLICABILITY

The present invention help environment protection from toxic organic compounds and carbon monoxide. The catalyst can work in catalytic plants for industrial gas cleaning and in special plants producing high potential heat via the catalytic combustion of fuels, natural gas in particular. 

We claim:
 1. A catalyst for the deep oxidation of organic compounds and carbon monoxide includes manganese compounds and alumina characterized in that in the active component of the catalyst manganese is presented by a defect non-stoichiometric manganese oxide-β-Mn₃ O_(4+x), where re 0.1≦×≦0.25, containing 80-95% of all manganese atoms, and by manganese aluminate containing 20-5% of manganese atoms and alumina is presented by the high-temperature forms α-Al₂ O₃ and (α+δ+θ)-Al₂ O₃, wherein the catalyst has the following composition:manganese compounds--2.7-11.5 mass % expressed in elementary manganese; alumina--the balance.
 2. A catalyst for claim 1 characterized in that alumina comprises

    ______________________________________     Al.sub.2 O.sub.3                   72-95 mass %     (δ + θ)-Al.sub.2 O.sub.3                    28-05 mass %.     ______________________________________


3. A catalyst for claim 1 characterized in that the active component has a monolith defect structure, particle size being 50-70 Å.
 4. A catalyst for claims 1, characterized in that the high temperature forms of alumina are the particles of irregular spatial configuration, and non-stoichiometric manganese oxide is presented by agglomerated smaller particles fixed on the surface of alumina particles by the layer based on the solid solution of manganese aluminate. 